1. Field of the Invention
The present invention relates to an internal combustion engine and, more particularly, to an exhaust port from a cylinder.
2. Brief Description of Prior Developments
U.S. Pat. No. 5,425,346 discloses a reason for selective exhaust gas recirculation based on time resolved exhaust gas hydrocarbon (HC) concentration at the exhaust port. A fraction of the exhaust gas rich in HC is recirculated through the piston and cylinder ports. The objective is to minimize the raw fuel from exhausting into ambient air. Instead the exhaust gas at an appropriate time is trapped and recirculated into the transfer passage for acting as a buffer medium between the fresh charge and burnt gas during scavenging process.
U.S. Pat. No. 5,361,732 discloses upper exhaust ports which are connected to a catalytic converter. The lower exhaust ports have flow that does not go through the catalytic converter. The two flows mix at an exhaust pipe. U.S. Pat. Nos. 3,240,194 and 4,920,931 show series of exhaust ports. U.S. Pat. No. 4,903,482 has two catalysts for treating different contents of gases released (high NOx and fuel in purge gas, respectively).
There is a desire to provides a muffler system which uses a lower amount of catalytic material and, hence, lowers the cost of the catalytic muffler. There is also a desire to provide a muffler system which improves heat issues within a catalytic muffler.